[T]he cloud-based service, which is rented to companies by the month, acts like a Web proxy, intercepting all incoming and outbound HTTP traffic from employees and scrubbing it for malware and online activity that violates company policy.

The company lets network managers create those policies with extremely granular controls over how their networks can be used. Detailed restrictions can be set over what kind of sites employees can visit and when they can visit them. For example, one company might say that marketing folks can only visit YouTube during lunch hour, and even then, they can only upload two megabytes to the site each day. Engineers might be blocked from visiting Facebook (since there is no telling what kind of anti-social trouble they will get into), but everyone else can. And everyone could be banned from visiting MySpace.